FIG. 1 illustrates one prior art apparatus 48 used to dispense liquid chemicals for semiconductor manufacturing. Apparatus 48 includes extractor tube 39 that passes through rubber stop 36 and extends into bottle 35. Liquids inside the bottle can be removed through feed tube 38, which is coupled to extractor tube 39 with clamp 37. Liquids can be extracted from bottle 35 by pumping or siphoning.
One disadvantage of apparatus 48 of FIG. 1 is that gap 40 between end 50 of extractor tube 39 and bottom 51 of bottle 35 inhibits the removal of all liquid from bottle 35. When relatively expensive chemicals are used with apparatus 48 as part of a manufacturing process, this loss of liquids can sometimes be costly. Moreover, the disposal of bottles containing even small amounts of certain chemicals sometimes raises environmental concerns.
Another disadvantage of apparatus 48 is that production sometimes must be stopped while bottle 35 is replaced with a bottle containing a new supply of the chemical being used in production.
Another disadvantage of apparatus 48 is that contamination is possible. When tube 38 is removed from bottle 35, extractor tube 39 is sometimes exposed to atmospheric contaminants and other contaminants external to bottle 35. If tube 39 is then placed in a new bottle 35, the contents of new bottle 35 are exposed to the contaminants on tube 39. In addition, once tube 38 is removed from bottle 35, extractor tube 39 may be covered with a residue of the liquid of bottle 35. If extractor tube 39 is then inserted in a different bottle 35 containing a different type of liquid, contamination might occur.
Moreover, the exposure of extractor tube 39 to the atmosphere for a period of time can sometimes lead to the crystallization of residual chemicals on extractor tube 39. The crystals can sometimes contaminate the liquid of new bottle 35. In addition, residues can sometimes clog extractor tube 39 partially or completely. The cleaning of tube 39 can sometimes result in the loss of production time.
One prior art delivery system employs an external probe (not shown) that is inserted into bottle 35 to measure the amount of liquid remaining in bottle 35. Any contaminants on the external probe can also lead to contamination of the liquid of bottle 35.
Another disadvantage of apparatus 48 is that air sometimes enters extractor tube 39 and feed tube 38. The air can cause air bubbles to form in the liquids being dispensed. Air bubbles should be removed from any liquid used in the production process to avoid misapplication of the liquids. Air bubbles are typically removed by running "dummy" or test wafers through the production process a number of times in order to "bleed" the liquid delivery system until air bubbles in the feed lines have been removed. This wastes the chemicals contained within the bottles, and certain chemicals can be relatively costly.
Yet another disadvantage of apparatus 48 is that the replacement of bottle 35 sometimes exposes individuals to hazardous chemicals, which can be a safety problem.